PRESS ARTICLE. Date: 7 August 2018

Transcription

1 PRESS ARTICLE Date: 7 August 2018 Flood Safety for Basement Spaces By Ir. Loo Chee Kin, Chairman of Mechanical Engineering Technical Division, The Institution of Engineers, Malaysia. Basements could be used to house important articles. In commercial buildings, these will be spaces used for mechanical and electrical utilities as well as carpark. Heavy imaging equipment, such as X-ray and MRI, will be placed here in a typical hospital. In residential houses, it could have collectors items; like vintage furniture, cars or wine cellar or a place for gaming or entertainment with high-tech audio-visual equipment. MRT line in major cities will have underground sections, hence there will be tunnel openings and underground stations. Water flooding into basement areas would not only cause damage to such equipment, but also economic loss in the building and long-term reputation. For example, if the basement of a mall is flooded and the chiller plant and electrical room become wet and submerged, not only will the equipment be damaged, but without chilled water and electricity, the mall simply cannot operate. In addition, such news will quickly be viral on social media. The primary step in flood safety for such basement spaces would be to keep the water out. But basements need opening for people and vehicular accesses. These have to be usually open and yet be able to be closed quickly in a flood situation. Any comprise in those openings would let the water enter the basement as water will flow through any gaps or opening. As water is subject to the laws of fluid mechanics, it could fill the whole basement over time. Flood gates are a way to block the entrances and doorways. The use of sandbags is not effective and would be time-consuming to build. It would be an ergonomics challenge to move hundreds of sandbags, each weighing tens of kilograms. The placement and stacking of sandbags would be a technical challenge, as the pile need to be stable and have minimal water seepage across it. After a flood event, much time would be needed to remove and store those sandbags.

2 Self-engineered gates may do the job, but there is no guarantee of performance and long-term durability. Certified flood gates will have to undergo several engineering test and evaluation. These could be full-scale water flowing simulation test as well as individual component test. Among the tests are; hydrostatic strength, leakage, cyclical, vibration, impact and wear resistant, salt spray corrosion, tensile and elongation, accelerate aging, compression, environment corrosion resistant, extreme conditions, abrasion resistant, tear and puncture. Deployable gate has to meet deployment time, wave-induced hydrodynamic load, overtopping, debris impact and current. Hydrostatic strength of the gate should be tested in the workshop, as a field testing would not be able to generate the required pressures on the pressure retaining parts, such as the seals and bladder. The usual acceptable leakage test by American Standards is 3 liters per minute per meter length. Otherwise, higher than allowed leakage test would overwhelm pumps inside the flood protected area. As these would be in contact with water, the salt spray corrosion testing would ensure any metal parts would not deteriorate prematurely. Conversely, compression and accelerate aging tests are crucial for plastic and rubber parts. The environment corrosion resistant extreme condition simulates the storage conditions, where the gate parts are subjected to moist carbon dioxide/sulfur dioxide mixture for several days and elevated temperature. The deployment time varies with the date design, and manufacturer must state the time, manpower, tools and resources to get the barrier installed in place. Since flood water is not still, the barrier had to withstand wave without significant deflection and additional leak, as well as water current flow at 2 m/s. Overtopping condition happens when a barrier floats, overturn or catastrophic failure when water flow over it. Debris impact is a rigorous test as the barrier has to withstand an impact by a simulated log, which would be a 43 cm diameter log, weighting 358 kg and moving at 8 km/hr. As there will be water seepage around the gates and infiltration through the basement structure, these need to be removed. Flood abatement pumps will be needed to pump the water into appropriate drains. Backwater valves would be needed on any discharge line from the building. This could be rain water, floor drains, sewers or sanitary lines. Otherwise back flow or water head in sewer lines would bring water into the basements. Floor or perimeter drains may need sluice gates as well. The flood plan should be documented in an emergency response plan. This plan should detail steps to be taken first and resources needed. Otherwise, time could be spent on unnecessary measures or less important. Having a checklist would ensure all the flood barriers are erected or in place, pumps checked, and the backwater valves or sluice gates checked. The plan should be triggered if there is flood warning from the authorities, local flood detection system or periods of heavy rainfall.

3 Wave testing in progress. Right side is a demountable flood panel being the flood gate. Flap gate for drain outlet.

4 Flood barrier on basement space windows Residential building protection

5 Automatic Hydraulic Flood Gate for Underground Facilities Protection For further information on this Press Article or The Institution of Engineers, Malaysia, kindly call the IEM Secretariat Office at / fax to or to About the Writer Ir. Loo Chee Kin is the Chairman of Mechanical Engineering Technical Division (METD) and Chairman of Disaster Risk Reduction Advisory Board (DRRAB) of The Institution of Engineers, Malaysia. As an engineer, he has carried out various natural hazard assessments and risk management with various clients and industries. About IEM The Institution of Engineers of Malaysia (IEM) is a civil society organisation established to promote the science and profession of engineering in any of its disciplines and to facilitate the exchange of information and ideas related to engineering. Founded in 1959 and with a membership of over 48,211 today, IEM constitutes one of the largest professional organisations in the country. Amongst its many roles, the Institution plays an active part in supporting various sustainable socio-economic development of the country and in nation building. It represents the aspirations of its members, acts in the best interests of the public of whom its members serve whilst upholding the standing and image of the profession.